Process of carburizing iron or steel



Patented June 24, 1930 UNITED STATES PATENT. OFFICE ROBERT G. GUTHRIE AND OSCAR J. WOZASEK, OF CHICAGO, ILLINOIS, ASSIGNORS TO PEOPLES GAS BY-TROIDUCTS CORPORATION,

OF ILLINOIS No Drawing.

The invention relates to new and useful improvements in the process of carburizing iron or steel by a gaseous treatment.

An. object of the invention is to'provide a process wherein a carbonaceous gas rich in carbon may be caused to flow over the iron or steel to be carburized and a carburization of the iron or steel of the desired character obtained without interfering soot precipitation on the surfaces of the iron or steel or the retort;

The invention in its broadest aspects relates to a process of carburizing iron or steel which consists in heating the iron or steel to an elevated temperature in a container or retort and subjecting said iron or steel while maintained at an elevated temperature to a carbonaceous gas which is rich in carbon. The carbonaceous gas is caused to flow over the iron or steel for a predetermined time interval depending upon the character of the gas used, the character of the material being treated and the conditions under which the treatment takes place. It is essential, however. that this interval of time shall be insuflicient. to cause interfering soot precipitation. The supply of the carbonaceous gas is discontinued for a period of time. During this interval the retort may be maintained in a substantially quiescentcondition or a supply of oxidizing gas may be introduced into the retort and caused to fiow over the iron or steel. During this quiescent period or period in which the oxidizing gas is supplied to the retort the iron or steel again becomes receptive to the carbonaceous gas without interfering soot precipitation. This interval of non-flow of carbonaceous gas is a det'inite interval predetermined by the charact er of the carbonaceous gas. the character of the material being treated, and the conditions under which the treatment takes place.

At the end of this period the retort is again supplied with the carbonaceous gas. The intermittent supplying of the gas for intervals of How and nontow continued until the desired carburization is obtained.

lteferring more in detail to the steps of the process: it 1500 pound cylinder retort OF CHICAGO, ILLINOIS, A CORPORATION PROCESS OF CARBURIZING IRON OR STEEL Application filed March 30, 1929. Serial No. 351.450.

supply of carbonaceous gas rich in carboir introduced into the retort. Acetylene, benzcne. gasoline or other hydrocarbons forming a carbonaceous gas rich in carbon or a mixture of these hydrocarbons may be used. The gas flows over the iron or steel While maintained at this elevated temperature and escapes through the outlet at the upper end of the container or retort. This flowing of the carbonaceous gas over the metal parts continues for a definite time interval determined by the character of the gas being used and the character of the metal being treated, and also by the temperature and pressure of the retort, after which the sup ply is temporarily discontinued.

The treatment of the metal with this rich carbonaceous gas is stopped short of interfering soot precipitation. \Vhen the supplyis discontinued, the retort is either held in a quiescent state or an oxidizing gas supplied thereto through a supply pipe at the bottom of the retort. Air, water vapor, oxygen, sulphur dioxide, carbon dioxide or any other oxidizing gas may beaised.

\Vhcn the oxidizing gas is admitted to the retort the efiiciency of the carbonaceous treatment is greatly increased. lVhile it is desirable under certain conditions to use the oxidizing gas, nevertheless, satisfactory results have been obtained by these quiescent intervals wherein no oxidizing gas whatever is supplied to the retort. At the end of this period when the retort is either heldin a quiescent state or an oxidizing gas is supplied, the retort is again supplied with the carbonaceous gas. The intermittent supplying of the carbonaceous gas for intervals of flow and non-flow is continued until the desired carburization of the iron or steel is obtained.

While we have described somewhat in de- 5 tail the carrying out of the process, it will be understood that the retort or container in which the iron or steel is treated may be of anydesired construction. Other forms of carbonaceous gas may be used, but it is essential that they shall be rich in carbon. The temperature and pressure in the retort may be varied and the time intervals of treatment may be varied depending upon the temperature and pressure in the retort and i the character of the gases being used and the material treated.

It will be understood, therefore, that the invention may be carried out in other ways than those specifically stated without departing from the spirit thereof as set forth in the appended claims.

Having fully described our invention, what We claim as new and desire to secure by Letters Patent, is

l. The process of carburizing iron or steel comprising heating the iron or steel to an elevated temperature in a retort, supplying said retort with a carbonaceous gas rich in carbon, and causing said gas to How over said iron or steel for a period of time short of interfering soot precipitation, discontinuing the supply of gas for a period of time, While the retort is maintained at an elevated temperature and until the iron or steel'is again receptive to the carbonaceous gas without interfering soot precipitation, and continuing intermittently this supplying of the gas for intervals of time until the desired carburization of the. iron or steel is 40 obtained. I

2. The process of carburizing iron or steel comprising heating the iron or steel to an elevated temperature in a retort, supplying said retort with a carbonaceous gas rich in carbon, and causing said gas to flow over said iron or steel for a period of time short of interfering soot precipitation, discontinuing the supply of carbonaceous gas and supplying said retort with an oxidizing gas while the retort is maintained at an elevated temperature, and causing the same to flow over the iron or steel for a period of time until the iron or steel is again receptive to the carbonaceous gas without interfering soot precipitation, and continuing alternately intermittently supplying of the carbonaceous gas and the oxidizing gas for intervals of time until the desired carburiz'ation of the iron or steel is obtained.

In testimony whereof, we aflix our signatures.

' ROBERT G. GUTHRIE. OSCAR J. WOZASEK. 

